Organic electroluminescent display devices (hereafter also referred to as organic EL display devices, or OLEDs) can be easily manufactured with thin profiles, have fast response times, and require no backlights, which is accordingly advantageous in terms of low power consumption. Organic electroluminescent display devices hold thus potential as display devices that can supersede liquid crystal display devices and CRTs (cathode ray tubes).
At present, red (R), green (G) and blue (B) pixels are separately applied, in organic EL display devices, by mask evaporation or ink-jet (IJ) methods. Specifically, as illustrated in FIG. 11, materials of functional material layers (organic functional layers) i.e. functional materials, are separately vapor-deposited for each pixel 300 of a respective color, by way of a slot mask, so as to cover each pixel 300 (pixel emissive section 310). As a result there are formed vapor deposition regions 320 that cover the pixels 300 of each color. If a slit mask is used, a stripe-like functional material is vapor-deposited for each pixel 300 of a respective color. If an ink-jet method is used, on the other hand, there is formed a bank that surrounds each pixel 300, and functional materials are applied within the banks. In this case, the coated regions within the banks correspond to the picture element emissive sections 310 in FIG. 11. Methods for forming coating-type R, G and B pixels using a solution such as those of ink-jet methods have attracted attention on account of the high material use efficiency that such methods afford. Ink-jet methods are used not only in the organic layers of the organic EL elements, but also to manufacture the color filter layers (colored layers) of color filter substrates, and functional thin films such as pattern wiring in metallic wiring substrates.
Instances where pixels of dissimilar colors (for instance, RGB) are formed by mask evaporation, however, involved significant technical problems in terms of the need for high-precision evaporation mask affixing technologies, as well as technologies for minimizing evaporation blur (technologies for clearly defining the boundaries between pixels of dissimilar colors). The increased mask weight that accompanies greater substrate sizes was also a problem.
On the other hand, formation of pixels of dissimilar colors using an ink-jet method involved significant technical problems in terms of the need for technologies for suppressing coating variability at each pixel, and the need for high-precision ink discharge technologies.
In conventional organic EL display devices it was thus difficult to form individual layers (films) for each R, G and B pixel. Therefore, major problems in terms of device, yield, cost and technology bedeviled the manufacture of high-definition organic EL display devices at a level of 300 ppi or greater, as currently afforded by liquid crystal display devices, and the manufacture of large organic EL display devices, at the 40-inch level. A demand existed thus for the development of simple and inexpensive methods for forming organic layers.
In this context, Patent Document 1 discloses, as a simple and inexpensive method of forming organic layers, a method for filling picture elements with an organic EL solution by capillarity. This method can also be used in high-resolution display devices. More specifically, separate R, G and B coating is accomplished by forming trenches for R, G and B pixels in such a manner that the leading ends of the respective trenches are at staggered positions, and by providing a stopper (photoresist) that hinders intrusion of organic EL solution, at the trenches for R and G pixels. Specifically, the method involves filling a B organic EL solution into a B pixel trench having the highest leading end; stripping next the stopper provided in the G pixel trench; filling next a G organic EL solution into the G pixel trench while preventing the G organic EL solution from coming into contact with the leading end of the B pixel trench; stripping next the stopper provided in the R pixel trench; and filling lastly an R organic EL solution into the R pixel trench.
Patent Documents 2 and 3 as well disclose methods for manufacturing organic EL display devices by capillarity. Patent Document 2 discloses a method for manufacturing an organic EL display device in which a trench (groove) formed in a photoresist is filled, by capillarity, with a dopant material. Patent Document 3 discloses a film formation method that involves forming an injection trench, which communicates with an opening at which a picture element is disposed, in a dielectric layer; and injecting a liquid, for instance an emissive layer material, into the injection trench, to cause thereby the liquid to flow, by capillarity, from the injection trench into the picture element. The methods of Patent Documents 2 and 3 enable separate coating, by capillarity, of pixels of at most two colors.